#!/usr/bin/env ruby
# frozen_string_literal: true

# Emit AST from parsed Ruby code by RuboCop.
#
# This is an alternative to `ruby-parser` shipped with `parser` gem.
#
# Usage:
#   rubocop-parse -e 'puts "hello"'
#   (send nil :puts
#     (str "hello"))
#
#   rubocop-parse -e 'puts "hello"' -v 3.0
#   (send nil :puts
#     (str "hello"))
#
#   rubocop-parse app/models/project.rb
#   (begin
#     (send nil :require
#       (str "carrierwave/orm/activerecord"))
#     (class
#       (const nil :Project)
#       (const nil :ApplicationRecord)
#       (begin
#         (send nil :include
#    ...

require_relative '../config/bundler_setup'

require 'rubocop'
require 'optparse'

module Helper
  extend self

  class << self
    attr_writer :ruby_version
  end

  def ast(source, file: '', version: nil)
    version ||= ruby_version

    ast = RuboCop::AST::ProcessedSource.new(source, version).ast
    return ast if ast

    warn "Syntax error in `#{source}`."
  end

  def pattern(string)
    RuboCop::NodePattern.new(string)
  end

  def help!
    puts <<~HELP

      Use `ast(source_string, version: nil)` method to parse code and return its AST.
      Use `pattern(string)` to compile RuboCop's node patterns.

      See https://docs.rubocop.org/rubocop-ast/node_pattern.html.

      Examples:
        node = ast('puts :hello')

        pat = pattern('`(sym :hello)')
        pat.match(node) # => true

    HELP

    nil
  end

  def ruby_version
    @ruby_version ||= rubocop_target_ruby_version
  end

  def rubocop_target_ruby_version
    @rubocop_target_ruby_version ||= RuboCop::ConfigStore.new.for_file('.').target_ruby_version
  end
end

def start_irb
  require 'irb'

  include Helper # rubocop:disable Style/MixinUsage

  puts <<~BANNER
    Ruby version: #{ruby_version}

    Type `help!` for instructions and examples.

  BANNER

  IRB.start
end

options = Struct.new(:eval, :interactive, :print_help, keyword_init: true).new

parser = OptionParser.new do |opts|
  opts.banner = "Usage: #{$PROGRAM_NAME} [-e code] [FILE...]"

  opts.on('-e FRAGMENT', '--eval FRAGMENT', 'Process a fragment of Ruby code') do |code|
    options.eval = code
  end

  opts.on('-i', '--interactive', '') do
    options.interactive = true
  end

  opts.on('-v RUBY_VERSION', '--ruby-version RUBY_VERSION',
          'Parse as Ruby would. Defaults to RuboCop TargetRubyVersion setting.') do |ruby_version|
    Helper.ruby_version = Float(ruby_version)
  end

  opts.on('-h', '--help') do
    options.print_help = true
  end
end

files = parser.parse!

if options.print_help
  puts parser
elsif options.interactive
  if options.eval || files.any?
    puts "Cannot combine `--interactive` with `--eval` or passing files. Aborting..."
    puts

    puts parser
    exit 1
  else
    start_irb
  end
elsif options.eval
  puts Helper.ast(options.eval)
elsif files.any?
  files.each do |file|
    if File.file?(file)
      source = File.read(file)
      puts Helper.ast(source, file: file)
    else
      warn "Skipping non-file #{file.inspect}"
    end
  end
else
  puts parser
end
